Polyoma virus functions important in the initiation and maintenance of cell transformation, and in turmorigenesis, will be studied. Altered polyoma viruses lacking restriction endonuclease sites in the "early" and "late" portions of the genome have been isolated, and partially characterized with respect to the extent of the genomic alteration that has occurred. The following biological properties of these viruses will be studied, a) ability to induce host DNA synthesis; b) ability to induce cell transformation, and c) ability to induce tumors. BIBLIOGRAPHIC REFERENCES: Anderson, D.M., and Folk, W.R. (1976) Iodination of DNA. Studies of the Reaction and Iodination of Papovavirus DNA, Biochemistry 15, 1022. Folk, W.R., and Bancuk, J.A. (1976) The Polyoma Genome in Hamster BHK 21-C13 Cells: Integration into Cellular DNA and Induction of the Viral Replicon, J. Virol. in press (October).